Adaptive lamp monitor with single piece sensor

Abstract

A lamp monitor provides a sense resistor for each lamp circuit as a special sense terminal member with a series resistance and sense terminals connected to a circuit board in a lamp monitor module. A multiplexing arrangement allows selection of the circuit to be monitored. The monitor samples the voltage across the series resistance by first connecting a capacitor across the sense terminals to be charged to the voltage and then disconnecting the capacitor from the sense terminals and connecting it across the input of an amplifier. The voltage across the lamps is sensed to provide a ratiometric reference for the digitizing of the amplifier output in an analog to digital converter; and a digital computer corrects the input digital signal with a stored non-linear normalization factor relating current to voltage in the lamps. The normalized value is compared with a predetermined percentage of a learned reference to determine lamp outage; and the learned reference is updated at a slowed rate when no lamp outage is detected.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. Lamp monitor apparatus for a vehicle lamp circuit having one or more lamps connected in parallel through a lamp switch to an electric power source, the lamp monitor apparatus comprising, in combination: a sense terminal member connected between the lamps and lamp switch, the sense terminal members comprising a single piece of electrically conducting alloy having a series resistive portion, a series terminal at each end of the series resistive portion and a sense terminal portion projecting from each end of the series resistive portion separately from the series terminal, the series terminals being connected to the lamps and lamp switch, respectively, to direct total lamp current through the sense resistor;   a circuit board having electrically conducting traces thereon electrically connected with the sense terminals of the sense terminal member, the circuit board having electronic components thereon connected to the traces for comparing the voltage across the sense terminals with a reference to determine lamp outage;   a case containing the sense terminal member and circuit board and including a heat sink adjacent the sense terminal member for dissipating the heat therefrom.   
     
     
       2. The lamp monitor apparatus of claim 1 in which the sense terminals extend through slots in the circuit board. 
     
     
       3. The lamp monitor apparatus of claim 2 in which the sense terminals are soldered to the electrically conducting traces of the circuit board at the slots through which they project. 
     
     
       4. The lamp monitor apparatus of claim 1 in which the series resistive portion and series terminals of the sense terminal member are aligned essentially parallel to the circuit board and the sense terminals are aligned essentially perpendicular to the series terminals. 
     
     
       5. The lamp monitor apparatus of claim 4 comprising a plurality of adjacent sense terminal members in which one of the series terminals of each of the sense terminal members forms part of a multiple circuit connector for a vehicle wiring harness to connect the sense resistive portions of the sense terminal members into a plurality of vehicle lamp circuits.